The power dissipation of integrated circuit chips, and the modules containing the chips, continue to increase in order to achieve increases in processor performance. This trend poses a cooling challenge at both the module and system level. Increased air flow rates are needed to effectively cool high power modules and to limit the temperature of the air that is exhausted into the computer center.
In many large server applications, processors along with their associated electronics (e.g. memory, disk drives, power, etc.) are packaged in removable drawer configurations stacked within a rack or frame. In other cases, the electronics may be in fixed locations within the rack or frame. Typically, the components are cooled by air moving in parallel air flow paths, usually front-to-back, impelled by one or more air moving devices (e.g., fans or blowers). In some cases it may be possible to handle increased power dissipation within a single drawer by providing greater air flow, through the use of a more powerful air moving device or by increasing the rotational speed (i.e. RPM) of an existing air moving device. However, this approach is becoming unmanageable at the frame level in the context of the computer installation (i.e. data center). The sensible heat load carried by the air exiting the frame will eventually exceed the ability of the room air conditioning to effectively handle the load. This is especially true for large installations with “server farms” or large banks of computer frames close together. In such installations not only will the room air conditioning be challenged, but the situation may also result in recirculation problems with some fraction of the “hot” air exiting one frame being sucked into the air inlets of a nearby frame. Furthermore, while the acoustic noise level of a powerful (or higher RPM) air moving device in a single drawer may be within acceptable acoustic limits, because of the number of air moving devices in the frame, the total acoustic noise at the frame level may not be acceptable. In addition, the openings required in the frame for the entry and exit of air flow makes it difficult, if not impossible, to provide effective acoustic treatment to reduce the acoustic noise level outside the frame. Finally, as operating frequencies continue to increase, we are approaching the point where electromagnetic (EMC) cross talk between tightly spaced computer frames is becoming a problem largely due to the presence of the openings in the covers required for air flow.
Recently, there has been an attempt to address some of the defects noted above by combining the air cooling approach with an air-to-water heat exchanger fixed within the server cabinet below the frame electronics. An example of such a system is Sanmina's EcoBay™442. The present invention builds upon prior approaches in ways that will become apparent below.
For the foregoing reasons, therefore, there is a need in the art for an improved and self-contained mechanism for cooling rack-mounted modular electronic units. Objects of the present invention include providing such a mechanism, while addressing, for example, the acoustic and EMC constraints noted above.